The railroad Tuesday canceled 11 morning-rush trains and seven during the evening rush, and rerouted several other trains. LIRR officials said similar service changes are likely through Friday as track repair work continues.

Four cars of an eight-car, non-passenger LIRR train went off the tracks just west of Forest Hills around 9 p.m. Monday.

No injuries were reported and the cause is being investigated, officials said.

"There's a lot of work ahead still, and we're asking for customers' patience," LIRR service vice president Joe Calderone said. "And the fact is we're actually running most of our service."

The derailment happened in "close quarters," partially on a bridge, he said. There are four main tracks between Jamaica and Penn Station, and the derailed train was blocking one of them.

By Tuesday afternoon, workers had re-railed two of the four displaced cars with the help of large locomotives.

Calderone said crews expected to clear out the remaining two derailed cars Tuesday night. He noted that much of the work will have to take place during off-peak hours to minimize the impact on commuters.

A YouTube video posted Tuesday by the MTA showed some damage and a track laying machine at work as LIRR's chief engineer Kevin Tomlinson described the difficulties in repairs.

"As the train derailed . . . the wheels fell in between the rail or fell on the outside of the rail, damaged the track," Tomlinson said.

The pace of work, impeded by passenger trains rolling past, should improve once rail traffic declines, he said: "I am working in between live tracks on both sides of us . . . We're trying to still run trains for our customers, and in our off hours, we're going to maximize the time and do as much as possible to get this back in service."

LIRR officials said that even after the derailed train is cleared from the tracks, much more work is needed before service can return to normal. The four derailed cars, each weighing about 62 tons, ripped through a quarter-mile of track, destroying 1,600 concrete rail ties and damaging the steel running rail and third rail.

Out of its usual 144 morning trains, the LIRR canceled 11 trains Tuesday, diverted five others to Atlantic Terminal in Brooklyn, and had four others terminate early at Jamaica.

Tuesday's evening cancellations included three trains on the Babylon line, and one each on the Port Jefferson, Long Beach, Far Rockaway and Port Washington lines. One Port Jefferson branch train that usually originates at Hunterspoint Avenue will instead originate at Jamaica.

There are fewer train cancellations during the evening rush than in the morning because the affected tracks are primarily used for westbound, morning service.

LIRR DERAILMENT-RELATED CHANGES

The 5:56 a.m. train from Babylon, due Penn at 6:59 a.m., will be diverted to Atlantic Terminal.

The 6:14 a.m. train from Massapequa Park, due Penn at 7:08 a.m., is canceled. Customers will be accommodated by the 6:12 a.m. train from Babylon to Penn, which will make an added stop at Rockville Centre; and the 6:26 a.m. train from Massapequa Park to Penn.

The 6:31 a.m. train from Lindenhurst, due Penn at 7:33 a.m., is canceled. Customers will be accommodated by the 6:32 a.m. train from Babylon, due Penn at 7:37 a.m.

The 6:57 a.m. train from Freeport due Penn at 7:40 a.m. is canceled. Customers will be accommodated by the 6:56 a.m. train from Wantagh due Penn at 7:43 a.m., making added stops at Freeport, Baldwin and Rockville Centre.

The 7:29 a.m. train from Freeport, due Penn at 8:13 a.m., is canceled. Customers will be accommodated by the 7:26 a.m. train from Wantagh, due Penn at 8:16 a.m., making an added stop at Freeport; and by the 7:10 a.m. train from Babylon, due Penn at 8:20 a.m., which will make added stops at Baldwin and Rockville Centre.

The 7:48 a.m. train from Wantagh, due Penn at 8:40 a.m., is canceled. Customers will be accommodated by the 7:29 a.m. train from Babylon, due Atlantic Terminal at 8:43 a.m.; and the 8:10 a.m. train from Freeport due in Penn at 8:50 a.m.

The 7:37 a.m. train from Babylon, due Penn at 8:48 a.m., will be canceled at Jamaica. Customers will be accommodated by the next westbound train to Penn.

The 8:10 a.m. train from Freeport, due Penn at 8:50 a.m., is canceled. Customers will be accommodated by the 8:25 a.m. train from Freeport, due Penn at 9:08 a.m., and by the 7:45 a.m. train from Babylon, due Penn at 8:56 a.m., which will make added stops at Freeport, Baldwin and Rockville Centre.

The 8:25 a.m. train from Freeport, due Penn at 9:08 a.m., will be diverted to Atlantic Terminal.

The 8:03 a.m. train from Valley Stream, due Penn at 8:42 a.m., is canceled. Customers will be accommodated by the 7:49 a.m. train from Far Rockaway, due Penn at 8:42 a.m., making added stops at Valley Stream, Rosedale, Laurelton, Locust Manor, Kew Gardens, Forest Hills and Woodside.

The 8:21 a.m. train from Far Rockaway, due Penn at 9:17 a.m., will be diverted to Atlantic Terminal.

HEMPSTEAD BRANCH:

The 6:58 a.m. train from Hempstead due Penn at 7:52 a.m. will be diverted to Atlantic Terminal. Customers will be accommodated by the 6:39 a.m. train from Ronkonkoma due Penn at 8 a.m. will make an added stop at Forest Hills.

The 7:12 a.m. train from Hempstead, due Penn at 8:03 a.m., will be diverted to Atlantic Terminal.

The 7:23 a.m. train from Long Beach, due Penn at 8:22 a.m., is canceled. Customers will be accommodated by the 7:39 a.m. train from Long Beach, due Penn at 8:32 a.m., and by the 7:49 a.m. train from Far Rockaway, due Penn at 8:42 a.m., which will make added stops at Valley Stream, Rosedale, Laurelton and Locust Manor.

The 8:03 a.m. train from Long Beach, due Penn at 8:54 a.m., is canceled. Customers will be accommodated by the 8:08 a.m. train from Long Beach, due Penn at 9:02 a.m.

MONTAUK BRANCH:

The 7:12 a.m. train from Speonk, due Hunterspoint Ave. at 9:11 a.m., will be canceled at Jamaica. Customers will be accommodated by the 9:12 a.m. train from Jamaica, due Hunterspoint Ave. at 9:28 a.m.

OYSTER BAY BRANCH:

The 7:13 a.m. train from Oyster Bay, due Long Island City at 8:34 a.m., will be canceled at Jamaica. Customers will be accommodated by the 8:19 a.m. train from Jamaica, due Long Island City at 8:44 a.m.

The 5:59 a.m. train from Port Jefferson, due Hunterspoint Ave. at 7:41 a.m., will be canceled at Jamaica. Customers traveling to Hunterspoint Ave. will be accommodated by the 7:31 a.m. train from Jamaica, due Hunterspoint Ave. at 7:49 a.m.

The 6:25 a.m. train from Hicksville, due Penn at 7:11 a.m., is canceled. Customers will be accommodated by the 5:44 a.m. train from Port Jefferson, due Penn at 7:20 a.m., making an added stop at Hicksville at about 6:41 a.m.; and by the 6:15 a.m. train from Huntington due Hicksville at 6:33 a.m., making added stops at Carle Place, Merillon Ave and New Hyde Park.

The 6:54 a.m. train from Central Islip, due Penn at 8:06 a.m., is canceled. Customers will be accommodated by the 6:56 a.m. train from Ronkonkoma, due Atlantic Terminal at 8:17 a.m.

The best way to be prepared for the unexpected is to be informed. The LIRR urges customers to:

Sign up for free email or text message service updates.

Visit its website mta.info for periodic service updates.

Call the LIRR Travel Information Center by dialing 511 and saying "LIRR." A taped message will describing current service conditions. Please be aware that the volume of calls at the Travel Information Center will dramatically increase during an emergency, and you may experience delays getting through.

Make sure you pick up a current LIRR timetable, as it will provide you with a frame of reference for train departure times at your station.

At your station, listen closely for public address announcements.

Depending on service conditions, Long Island Rail Road employees will be on hand to answer questions about service and, if necessary, alternative means of travel.